The present invention relates to determining the presence of small particles, such as those from Diesel exhaust in an air sample.
Research has shown that coal mines utilizing diesel powered equipment produce a bimodal distribution of aerosol particles. Diesel exhaust particles are primarily smaller than about 0.8 microns, while coal dust particles are larger.
It is important to measure the concentration of diesel and coal particles in order to monitor the air quality of air that is being breathed. Various samplers have been advanced to collect the respirable size particles in a mine.
U.S. Pat. No. 4,941,899 illustrates a personal aerosol sampler that has a two stage operation with a standard cyclone separator providing removal of large nonrespirable particles before the air being sampled was introduced into a secondary cyclone sampler. The secondary sampler initially separates out particles below about 0.8 microns from larger particles, and has a cup for collecting the larger particles for analysis. It has been found that this type of a separator can become overloaded, or some large particles can be re-entrained and then will be collected with the smaller diesel particles so that erroneous results may be given.